Along with the recent development in the electronic equipment, the wiring substrates of the electronic component devices for use in the electronic equipment have been required to have smaller sizes, higher performance, and the like. In order to respond to such requirement, the electronic component built-in substrates in which the electronic component is built in the wiring substrate have been put into practical use.
In one example of such electronic component built-in substrate, the electronic component is arranged in an opening portion of a core substrate, and build-up wirings are formed on both faces side of the core substrate.
A related art is disclosed in Japanese Laid-open Patent. Publication No. 2011-216740.